Fuel injection apparatus, a piston engine and method of operating a piston engine

Abstract

A fuel injection apparatus for a piston engine includes a fuel injector body in which an injector needle is provided, which injector needle is arranged to prevent or allow fuel injection flow from the injection apparatus based on the position of the injector needle. The position is effected by a pressurized control fluid so that by applying the pressurized control fluid the needle may be urged towards its closed position and by reducing the pressurized control fluid the needle may be allowed to move away from its closed position. The injection apparatus includes a flow path for the control fluid, wherein the flow path for the control fluid comprises a restriction section providing a restriction effect to the control fluid flow. The restriction section includes at least one temperature-effected member providing a temperature-dependent restriction effect.

The invention claimed is: 
     
       1. A fuel injection apparatus for a piston engine comprising:
 a fuel injector body in which an injector needle is provided, which injector needle is arranged to prevent or allow fuel injection flow from an injection apparatus based on a position of the injector needle, which position is effected by a pressurized control fluid in a control space; 
 the fuel injector body comprising an injector space, into which the injector needle is arranged, which injector space is provided with a fuel inlet port and fuel injection spray hole orifices at a first end of the injector space, through which the fuel may be injected under control of the injector needle, 
 wherein a second end of the injector needle is arranged to border the control space, which control space is connectable with a low pressure side of the fuel injection system via a flow path for the control fluid, 
 wherein the flow path for the control fluid comprises a restriction section for restricting a flow of the control fluid, the restriction section bounded by a valve plate and a control plate, and 
 wherein the control plate is separate from and movably received in a collar part, the control plate sealingly engageable with the valve plate to seal the control space in an non-injection position, the control plate comprises an orifice, 
 the collar part bounding the control space when the control plate is completely separated from the valve plate, the collar part at least partially circumferentially surrounding the injection needle, 
 the restriction section comprising the orifice in the control plate and an outlet channel of the valve plate, 
 the control plate having a different coefficient of thermal expansion than the valve plate allowing a change in a restriction effect of the restriction section in response to a change of a temperature of the valve plate and the control plate. 
 
     
     
       2. A fuel injection apparatus according to  claim 1 , wherein the control space is bordered by the collar part encircling at least partly the injector needle. 
     
     
       3. A fuel injection apparatus according to  claim 2 , wherein the collar part encircles at least partly an end of the injector needle. 
     
     
       4. A fuel injection apparatus according to  claim 2 , wherein the restriction section comprises a gap between the outer surfaces of the injector needle and the collar part. 
     
     
       5. A fuel injection apparatus according to  claim 1 , wherein the first member is of ceramic material and the second member is steel. 
     
     
       6. A piston engine having a common rail fuel injection system, wherein the common rail fuel injection system comprises a fuel injection apparatus according to  claim 1 . 
     
     
       7. A piston engine according to  claim 6 , wherein the piston engine comprises a cooling system arranged in operational vicinity of the fuel injection apparatus. 
     
     
       8. A piston engine according to  claim 7 , wherein the piston engine comprises a cooling system arranged in operational vicinity of the body of the fuel injection apparatus. 
     
     
       9. A method of operating a piston engine with a common rail fuel injection system comprising a fuel injector apparatus according to  claim 1 , in which method the piston engine is operated so that after starting the engine, emission of at least one predetermined substance is measured from the exhaust gases of the engine, wherein at least until the engine has reached its operational temperature the cooling system of the engine is controlled to have effect on the temperature of the fuel and/or the fuel injection apparatus in order to control the at least one temperature-effected member providing a temperature-dependent restriction effect to the control fluid flow effecting on the position of the injector needle.